This invention relates to an air filter, and particularly to an air filter for the intake air of an internal combustion engine.
U.S. Pat. No. 4,720,292 discloses an air filter having a housing provided with an axial outlet opening and an essentially open second end which is closable by a removable cover. An air inlet opening is provided on the circumference of the housing. The housing accommodates an essentially cylindrical filter element having an inner support tube and a filter having an outer support tube, with the inner filter element being arranged coaxially in the housing. The filter element is sealed on the housing by an annular end disk which has an essentially cylindrical surface directed radially inward and which is pushed over an inner section of the outlet part. It is known that filter inserts in air filters are replaced after a certain operating time. Depending on the dust load, the service life of a filter may vary from a few days—e.g., construction machines—up to several months.
One disadvantage of the known state of the art can be seen in the fact that a relatively large housing is needed for the filter insert and takes up an unnecessarily large amount of space in the clean air area. The known filter systems for internal combustion engines are usually installed in the vicinity of the engine, usually in the engine compartment. However, it is becoming increasingly difficult to situate the air filter system in this area because the available installation space has been dwindling. Space is very limited in commercial vehicles in particular, especially in tractors, due to the extra functions provided in the engine compartment, e.g., hydraulic and pneumatic elements. Access to these systems is hindered by an air filter system situated in the engine space near the engine. In addition, placing the air filter in the engine compartment puts the intake in a dirty area of the vehicle, so that the air filter is exposed to such an elevated particulate burden that the service life of the filter is greatly reduced.
In this regard, German Patent DE 79 02 819 proposes to provide an intake air purifying element as an external element mounted on the body of a truck, whereby the element includes a prefilter and water separator, a cyclone and an air filter. However, this embodiment is dependent on the individual construction of the bodies of various trucks and is thus greatly limited with regard to freedom of placement, and in many cases it cannot be used at all in agricultural machines, for example, with their special bodies.